Tension roll drives



F 1943- a. P. LESSMANN 2,310,098

TENSION ROLL DRIVES Filed July 5; 1941 WlTNESSES: INVENTOR a; Q jar/70rd 14 13550900 2,3lllgl9d TENSION ROLL DRIVES Gerhard P. Lessmelm, Wllkinsburg, Pm, cssigcor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, 19s., a corporation of Pennsylvania Application July 5, 1941, Serial No. 401,160

(010 Sli -=32) 6 Claims lily invention relates, generally, to plural ten slor "oil drives and, more particularly, to electricol. drive systems for pairs of tension rolls for tenslonl'ng a strip of material while it is in moticn.

operation of steel strip rolling mills, it is common practice to subject the strip to tension as it is acted upon by the mill. Tenslonlng devices employed on the delivery and entry sides of the will often. tolse the form of a pair of independent separately driven rolls disposed between the reducing rolls and the reel, and over which the strip passes in a. partial wrap. The tension applied to the strip by such tension rolls dep nds upon the frictional engagement of the strip'with the tension rolls.

it has been found desirable to drive the two tension rolls of such tensionlng devices with sepnlotors and to operate these motors in se-- ries oil; relation Irom s single source of power. in operating the tsnsioning roll motors in series circuit relation, it has been found neoto either divide the load between the motors or to provide 9, system for maintaining the l otion between the potentials across the arcs of the motors, in order to insure rotation of tooth of the motors in the event that one cl" the motors should become much more heavily loaded the other.

As an extreme example of the necessity for menus for insuring rotation of both or the series connected tension roll motors, when it is necessary to polish or resurface the tension rolls, rolls are driven idly without any strip in contact with them and st grinding device, such emery paper, is held against the rolls as they rotated, Durh'lg this resurfacing operation, it very much load is placed on the tension roll that is losing resurfaced, its driving motor will stall and the idling roll motor will speed up because the transfer of most of the available potential to the idling roll motor. A similar condition sometimes exists when the drive motor for the tension roll nearest the roll stand is much more heavily loaded than the drive motor for the tension roll nearest the reel. Under these conditions, the more heavily loaded motor tends to slow dot-m end stall, while the more lightly loaded motor tends to speed up and may even cause slipping between the tension roll and the strip and consequent scratching of the strip surface.

It is an object of my invention to provide an electric drive system for the tension rolls of a plural tension. roll. strip tensioning device which shall function to provide positive rotation of the several tensioning rolls regardless of the degree of unequal distribution of load between the tenslo ing rolls.

Another object oi the invention is to provide an electric drive system for the tension rolls of a plural tension roll strip tensloning device which shall function to maintain sufflcient potential on the tension roll drive motors to insure their rotation under all conditions of load distribution between the drive motors.

These and other objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawing, the single figure of which is a diagrammatic view of a portion of a strip rolling mill, strip tensioning rolls and a strip reel end the electrical drive and control system therefor emloodymg the principal features of my invention.

In practicing my invention, as a, strip 2 is delivered from a strip rolling mill 4 and wound on a strip reel 6, it passes over tensloning rolls 8 and I8, as indicated in the drawing. The reel 6 is driven by a, motor l2 to apply the desired reeling tension to the strip, and the tensioning rolls 8 and iii are driven by motors M and i6, respectively. The motors it and 16 are connected in series circuit relation to be energized by a continuously driven generator l8. Dynamoelectrlc machines 20 and 22 are connected in parallel circuit relation with the motors i4 and i6, respectively, and are mechanically connected together by a shaft 24. The dynamo-electric machines 26 and 22 normally run idly as motors in series circuit with the generator ill, but when there is suficient unbalance of the load between the motors H and i6, one of the dynamo-electric machines runs as a, motor driving the other as a generator to compensate for the load unbalance.

Considering the invention more in detail, the reel motor i2 may be connected to any suitable source of power, and may be controlled by a current regulator to maintain substantially constsnt winding tension on the strip 2 in a man ner similar to that explained in the patent to A. F. Kenyon, No. 2,214,617, issued September 10, 1940. The field windings of the reel motor i2, the mill motor, the tensioning roll motors I l and IS, the generator l8, and the dynamo-electric machines 20 and 22 may be connected to any suitable source of direct-current power, as indicated by the plus and minus signs, and are provided with variable resistors in their circuits to vary the excitation of the machines as desired.

The series energizing circuit for the tension circuit relation, and the roll motors l4 and 16 extends from one terminal of the generator l8 through a conductor 26, the armature of the motor IS, a conductor 28, the armature of the motor l4, and a conductor 30 to the other terminal of the generator I8. The armature of the dynamo-electric machine 22 is connected in parallel circuit relation with the armature of the motor IS in a circuit which extends from the conductor 26 through a conductor 32, the armature of the dynamo-electric machine 22, and conductors 34 and 36 to the conductor 28. A similar circuit connects the armature of the dynamo-electric machine 20 in parallel circuit relation with the armature of the motor I 4 in a circuit which extends from the con= ductor 30 through conductor 38, the armature of the dynamo-electric machine 20, and conductors 34 and 36 to the conductor 28.

In the operation of the system, the winding reel 6 applies only that tension to the strip 2 which is desired as it is wound on the reel 6. The tensioning roll i will apply a tension to the strip 2 in addition to the winding tension, so that the tension on the strip between the tensioning rolls 8 and ill will be equal to the sum of the tensions applied by the reel 6 and the tensioning roll i 9. The tensioning roll 8 will apply still further tension to the strip 2, and the tension applied to the strip 2 as it is delivered from the roll stand 4 will be equal to the sum of the tensions applied to the strip by the reel 6, the tensioning roll I0 and the tensioning roll 8. It will be seen that these conditions will warrant .the tensioning roll 8 applying a greater tensi in to the strip 2 than the tensioning roll iii, since there will be greater pressure of the strip 2 on the roll 8 than on the tensioning roll it as a result of the tension on the strip 2 between the tensioning roll 8 and the roll stand 4 being greater than the tension between the tensioning rolls 3 and It.

The motors l4 and it will, therefore, normally so adjusted as to cause the motor M to carry a greater proportion of the load than the motor 56. Should the proportion of the loads on the motors l4 and I6 become much greater than de sired for any reason, there would be a tendency of the motor 14 to take less of the potential output of the generator i8, and the motor 56 to take more of the potential output of the generator l8, since the motors i4 and !6 are connected in series motor l4 would tend to stall, while the motor I8 would tend to speed up and may even speed up sufliciently to slip the tensioning roll In on the strip 2, thertby damaging the surface of the strip 2 and the surface of the tensioning roll 10.

In' the operation of the system, the dynamo electric machines 20 and 22 normally run idle as motors in series circuit relation. However, when there is an undesirable unbalance of the potentials across the armatures of the motors I4 and IS, a similar unbalance of potential will exist across the dynamo-electric machines 20 and 22, and the dynamo-electric machine having the higher potential across its armature will run as a motor to drive the other dynamo-electric machine as a generator to thereby boost the potential of the tensioning roll motor having the deficiency in energizing potential on its armature.

As an example, should the load on the tensioning roll motor I6 decrease, the potential across its armature would increase, and the potential across the armature of the tensioning roll motor [4 would decrease. This would cause the 7 thereby prevent the motor M from dynamo-electric machine 22 to drive the dynamoelectric machine 20 as a generator to thereby increase the potential acting on the armature of the motor 5 6 to compensate for the decrease in potential on the armature of the motor it due to the unbalance of loads on the motor I6 and stalling. At the same time, the increase load taken by the dynamo-electric machin 22 acting as a motor will cause a drop in the potential across the armature of the tensioning roll motor #6 to prevent the motor I 6 from overspeeding and slip ping the tensioning roll ID on the strip 2.

The variable resistors in the field windings of the dynamo-electric machines 29 and 22 and the field windings of the tensioning roll motors l4 and It may be adjusted as desired to provide for any desired load division between the motors M and i6.

It is to be understood that the system will work equally as well on the entering side of the strip rolling mill with the motors Id and I6 acting as drag generators to provide back tension on the strip 2 as it is fed into the mill. It is to be further understood that the number of strip tensioning rolls and associated drive motors and dynamo-electric machines are not limited to two, as described in detail hereinbefore, but that any number of tensioning rolls that is required to produce the desired strip tension may be employed and controlled by individual drive motors connected in series circuit relation and associated dynamo-electric machines connected in parallel circuit relation therewith and connected in driving relation with each other.

It will be seen that I have provided an electric drive system for the tension rolls of a plural strip tensioning device which shall function to maintain sufiicient potential on the tension roll drive motors to insure their rotation under all conditions of load distribution between the drive 1 motors, and to provide positive rotation of the several tensioning rolls regardless of the degree of unequal distribution of load between the tensiom'ng rolls.

In compliance with the requirements of the patent statutes, I have shown and described herein a preferred embodiment of my invention. It is to be understood, however, that the invention is not limited to the precise construction shown and described, but is capable of modification by one skilled in the art, the embodiment herein described being merely illustrative of the principles of my invention.

I claim as my invention:

1. In a strip tension adjacent work devices a moving strip of material as it the work devices, a pair of tensioning rolls disposed between the work devices and over which the strip passes in a partial wrap as it passes between the work devices, a pair of main dynamoelectric machines each associated with a different one of said tensioning rolls, means mechanically connecting the associated tensioning rolls and dynamo-electric machines in driving relation with each other, circuit means connecting said main dynamo-electric machines to a source of power in series circuit relation, a'pair of auxiliary dynamo-electric machines, means mechanically connecting said auxiliary dynamo-electric machines in driving relation with each other, and circuit means electrically connecting each of said auxiliary dynamo-electric machines in parallel control system, a pair of. successively acting upon extends between circuit relation with a different one of said main dynamo-electric machines.

2. In a strip tension control system, a. pair of adjacent work devices successively acting upon a moving strip of material as it extends between the work devices, a pair of tensioning rolls disposed between the work devices and over which the strip passes in a partial wrap as it passes between the work devices, a pair of main dynamoelectric machines each associated with a different one of said tensioning rolls, means mechanically connecting the associated tensioning rolls and dynamo-electric machines in driving relation with each other, circuit means connecting said main dynamo-electric machines to a source of power in series circuit relation, 8. pair of auxiliary dynamo-electric machines, means mechanically connecting said auxiliary dynamo-electric machines in driving relation with each other, circuit means electrically connecting each of said auxiliary dynamo-electric machines in parallel circuit relation with a difierent one of said main dynamo-electric machines, and control means for said main and auxiliary dynamo-electric machines for producing any desired load distribution between the main dynamo-electric machines.

3. In a strip tension control system, a pair of adjacent work devices successively acting upon a moving strip of material as it extends between the work devices, a plurality of tensioning rolls disposed between the work devices and over which the strip passes in a partial wrap as it passes between the work devices, a plurality of main dynamo-electric machines each associated with a different one of the tensioning rolls, means mechanically connecting the associated tensioning rolls and dynamo-electric machines in driving relation with each other, circuit means connecting said main dynamo-electric machines to a source of power in series circuit relation, a plurality of auxiliary dynamo-electric machines, means mechanically connecting said auxiliary dynamo-electric machines in driving relation with each other, and circuit means electrically connecting each of said auxiliary dynamo-electric machines in parallel circuit relation with a different one of said main dynamo-electric machines.

4. In a strip tension control system, a pair of adjacent work devices successively acting upon a ,moving strip of material as it extends between the work devices, a plurality of tensioning rolls disposed between the work devices and over which the strip passes in a partial wrap as it passes between the work devices. a plurality of main dynamo-electric machines each associated with a difierent one of the tensioning rolls, means mechanically connecting the associated tensioning rolls and dynamo-electric machines in driving relation with each other, circuit means connecting said main dynamo-electric machines to a source of power in series circuit relation, a plurality of auxiliary dynamo-electric machines, means mechanically connecting said auxiliary dynamo-electric machines in driving relation with each other, circuit means electrically connecting each of said auxiliary dynamo-electric machines in parallel circuit relation with a different one of said main dynamo-electric machines, and control means for said main and auxiliary dynamo-electric machines for producing any desired load distribution between the main dynamo-electric machines.

5. In a system for subjecting a strip of material to tension as it passes between two adjacent work devices, a plurality of tensioning rolls over which the strip passes in a partial wrap as it passes between the work devices, a plurality of motors each connected in driving relation with a different one of said tensioning rolls, circuit means connecting said motors to a source of power in series circuit relation, a plurality of dynamoelectric machines, means mechanically connecting said dynamo-electric machines in driving relation with each other, circuit means electrically connecting each of said dynamo-electric machines in parallel circuit relation with a different one of said motors, and control means for said motors and dynamo-electric machines for producing any desired load distribution between the motors. I

6. In a system for subjecting a strip of material to tension as it passes between two adjacent work devices, a plurality oi tensioning rolls over which the strip passes in a, partial wrap as it passes between the work devices, a plurality of motors each connected in driving relation with a different one of said tensioning rolls, circuit means connecting said motors to a source of power in series circuit relation, a plurality of dynamoelectric machines, means mechanically connecting said dynamo-electric machines in driving relation with each other, circuit means electrically connecting each of said dynamo-electric machines in parallel circuit relation with a different one of said motors, and control means for said drag generators and dynamo-electric ma.- chines for producing any desired load distribu tion between the drag generators.

GERHARD P. LESSI LANN. 

